1. Field of the Invention
The present invention relates to an automotive headlamp apparatus and a method of controlling an automotive headlamp apparatus, and, more particularly, to illumination control using a light source for high beam illumination.
2. Description of the Related Art
Generally, an automotive headlamp apparatus is provided with a light source for high beam illumination used for emitting an upper beam and a light source for low beam illumination for emitting a lower beam. Of these, a high beam is required to provide distant illumination with the maximum brightness permitted within the brightness range defined in the relevant law. Meanwhile, care should be taken so that oncoming vehicles, vehicles in front, or pedestrians do not experience an uncomfortable glare. A low beam forms a light distribution pattern that allows for reduction of glare. A high beam, on the other hand, forms a light distribution pattern that gives priority to ensuring a field of view for the driver and does not allow for reduction of glare as much. In this regard, an automotive headlamp apparatus is provided with a switch for switching between the low beam mode and the high beam mode. The driver selects one of the beam modes depending on whether there are oncoming vehicles or pedestrians, indicating whether to give priority to securing the field of view by using the low beam light source and the high beam light source or to prevention of glare by using only the low beam light source.
There is also proposed an automotive headlamp apparatus in which a single lamp unit forms a plurality of light distribution patterns. For example, the illumination device disclosed in JP 2001-266620 is provided with a large number of semiconductor light sources arranged in a matrix. The large number of semiconductor light sources are individually controllable and form different partial regions. The semiconductor light sources are individually controlled as needed to form a desired light distribution pattern and allow switching between the low beam mode and the high beam mode.
For example, drivers use a high beam because they feel that information indicating the pattern of the road far ahead, whether there are obstacles, or whether there are oncoming vehicles or pedestrians is not sufficient only by using a low beam while driving at night and so aim to obtain as much information as possible. Meanwhile, care should be taken not to let oncoming vehicles, vehicles in front, or pedestrians experience a glare. As mentioned before, the related-art headlamp apparatus is configured to entirely turn off a high beam light source in order to reduce a glare. In this case, the function of a high beam is temporarily prevented from being exhibited. We have come to be aware that there is a room for improvement in view of the driver's need for a sufficient field of view. Having to entirely turn on and off a high beam also makes drivers reluctant to use it on city streets.
The illumination device disclosed in JP 2001-26620 is capable of forming a plurality of light distribution patterns using a large number of semiconductor light sources arranged in a matrix and so is capable of more meticulous illumination control than just turning on and off a high beam. However, the illumination device disclosed in JP 2001-26620 requires controlling a large number of semiconductor light sources individually to form partial regions that define desired light distribution patterns. Accordingly, the number of control lines would be enormous and control would become complicated. Moreover, requirement for a large number of semiconductor light sources results in an increase in the cost for components and complexity of assembly.